Paper manufacture



Sept. 20, 1932. w. J. ZIMMERMAN PAPER MANUFACTURE Filed Aug. 16, 1928Patented Sept. 20', 1932 UNITED .sTAras 'WALTER iLflZIMMERMAN, OFlDAYTON, 'OHIO, ASSIGNOR '10 MEAD PAPERIBOARD CO PATENT orFIcE 1PORATION, OF WILMINGTON, DELAWARE, A CORPORATION OF DELAWARE PAPERMANUFACTURE This invention relates tothe manufacture of paper, and thelike, andparticularly to the preparation of'pulp for use-infsuchmanufacture.

One of the-principal objects of this invention is to provide a method oftreating fibrous materials to forma superior pulp having unusualstrength with a large yield, and in which desired uniformity of the pulpproduct is obtained. a I

Another object of this invention is to provide a method of pulpingfibrous materials, such as hard woods which have heretofore beendifficult and impractical to treat with the hitherto knownpulping'processes, to form a satisfactory pulp with a high yield for themanufacture of paper or board and the like.

Another object-of this invention is to provide apparatus .for carryingout the above method, which apparatus is simple in construction, andhighly effective and readily controlled in operation.

Other objects and advantages of this invention will be apparent from thefollowing description and a from the accompanying drawing, and theappended claims.

In the drawing, the single figure is a; diagrammatic view of apparatusconstructed for carrying out the method of this invention.

According to this invention the fibrousmaterials are first cooked, orotherwise treated with chemicals, to loosen the bonding material holdingthe fibers in their natural asso-- ciated form, after which the treatedfibrous materials are subjected to mechanical disintegration ordefibering to so separate the fibers that they will form a suitablepulp, this mechanical defibering action being controlled in accordancewith operating variations in the characteristics of the treated fibrousmaterials and coordinated therewith to give an ultimate pulped productof substantially uniform characteristics. For purposes of illustrationof preferred embodiment of the method and apparatus for practicing themethod, the invention is hereinafter described in connection with thetreatment of chestnut wood,and more particularly of leached chestnutchips from which tannic acid has been e tracted. z

Application filed August '16, 1928. Serial No. 299,982.

In treating such materials the chestnut chips are first given a chemicaltreatment or cooking which is effective to soften them, but is purposelyso limited in its eifects that any considerable defibering or separatingof the Wood into its ultimate fibers does not result, with resultinghigh strength and yield of the ultimate product. In actual commercialoperations according to this invention, this treatment is what is calledan incomplete digestion and it is so controlled that the I chips retainsubstantially their original form, but may be thereafter readilydefibered with properly coordinated mechanical treatment. Thisincomplete digestion may vary considerably depending upon the fibrousmaterial being treated and the ultimate product desired; but in thecommercial operations referred to a so-called semi-chemical cook,hereinafter point such as is possible where a substantially completedigestion is effected and the incrustants are primarily dissolvedleaving the fibers in separated condition. In fact different batches ofthe same material subjected to this semi-cooking may vary considerablyin character, due to variations in the cooking action resulting fromvariable factors wh1ch.are I practically indeterminate and not easilycontrolled. The character of the cooked material may vary considerablyfrom a more complete- 1y cooked material or one in which more of theincrustants and lignins have been removed and a higher degree ofhydration of the fibers has been effected, and which is hereinaftertermed a ft cook, to a less completely cooked material or one in which alarger percentage of the incrustants and-lignins remain in the materialand a lesser degree of hydration of the fibers has been effected, andwhich is hereinafter termed a hard cook.

The fibrous material resulting from the semi-cook is then subjected tomechanical i treatment to complete the pulping of the material and toprovide a pulp product of desired uniformity irrespective of varlatlonsin the characteristics of the cooked material.

- This is accomplished by-subjecting the cooked the cooked material tothe action of a rodm ll,

after which it is passed through a Jordan engine. The rod mill effectsapoundlng,

' rubbing and shredding action which disintegrates the material andhydrates the fibers without objectionable cutting of the fibers.Thesubsequent Jordan treatment effects what may be termed a brushing outtreatment, which sufficiently separates the material into its ultimatefibers, and prepares it for proper\ formation on the paper machine.These treatments are coordinated in accordance with the characteristicsof the cooked material as received from the cooking digester, or thelike, to secure a final pulp product of the desired uniformcharacteristics. Vhere the cooking treatment produces a hard cook, orone in which a lesser degree of hyd ation of the fibers is obtained, thedegree of the rodmilling treatment is increased by relatively prolongingthe time of such treament to complete the hydration of the fibers toa-desired point, and the degree of ordaning treatment is lessened byfreeing or opening up the setting of the Jordan. Conversely when a softcook is obtained, the degree of treatment in the rod mill is reduced byrelatively shortening the time of such treatment, while the setting ofthe Jordan is tightened up to give a more rigorous action on the fibersto thereby produce a stock in which the lumps are effec: tively reduced,producing a more uniform consistency of the fibrous stock. I By a propercontrol and coordination of these mechanical treatments in accordancewith the. character of the cooked material, a final pulp product ofsubstantially uniform characteristics is obtained which is adapted to beformed directly into paper or board of uniform quality.

Referring to the drawing, in which a preferred embodiment of apparatusfor carry ing out the above method is disclosed, a conveyor for rawfibrous materials is indicated cores and the like, which have heretoforeproved extremely difiicult and impractical to treat by conventionalpulping processes to give a satisfactory grade of pulp of sufficientstrength and yield. This invention opens up a field of use for wastewood, such as from furniture factories which contains a propor- The rawfibrous material is cooked, preferably with an incomplete digestion .orsemichemical cook which gives an exceedingly high yield and a product ofunusual strength. In the semi-chemical cook, Ver satisfactory resultsare secured with an aqueous solution of a normal sulphite containing asalt of a weekly ionized polybasic acid, such as a mixture of sodiumsulphite and sodium bicarbonate. The cook is carried out in two stages.The charge of wood chips is added to the digester and the chips afterbeing preferably steamed for about half a ho to remove air from the woodto faciliw ii npregnation with liquor are then submerged in the cook ingliquor and the temperature is brought up to approximately C. to (3..with steam for a length of time to secure desired impregnation of theliquor within the Wood, this being termed the impregnation stage.

A treating time of about two hours gives satisfactory resultsinthisfirst stage. The unabsorbed liquor is then drawn off .and theliquor-saturated material remaining in the a digester is then raised toa temperature of approximately C. to C. for a period action with theincrustants and ligneous material takes place with resultant softeningof the chips. According to the length of time and temperature of thisfinal heating treatment, the characteristics of the fibrous stock aredetermined such as whether it can be easily hydrated or not, itsbulkiness, and whether it will form a hard or soft sheet, andthe like. V

Reference is herein made to the patent to FrancisG. Rawling, 1,673,089,issued June 12, 1928, which discloses and claims a semichemical cook ofthisccharacter.

In practical operation, the character of the cooked material produced bysuch a semichemical cook varies. This is due to certaiii variablefactors in the cooking, such as the character of the steam as to whetherit is dry. wet or superheated, the moisture content of the chips chargedinto the digester, the, amount of CO formation in the digester duringthe coking which sets up what is termed a false pressure or a pressurewhich is not the result of the introduction of steam, and other factorswhich so far it has been found commercially impracticable to controlwithin suitably narrow limits. The result is that the characteristics ofthe cooked materials'vary from a hard cook to a soft cook, which varyingcharacteristics would show up in the finished pulp to give objectionablevariationsin the freeness of the stock, the hardness, its degree ofhydration, and the like to give a paper or board of non-uniform quality.These variations may be compensated for and a uniform final productobtainedby coordinating the steps ofthe subsequent defibering, bycoordinating the rod milling and ordaning treatments.

The cooked material is discharged from the digester'into a dump tank 15.The ma whereby it is easily handled at high consistency. The mass ofsoftened chips discharged into the dump tank 15 is then washed to removeresidual liquor. This is preferably accomplished by introducing washwater into thedigester and then permitting this liquor to discharge uponthe chips within the dump tank 15. The washing is completed by theintroduction of any additional wash water neededas by a hose onto thesurface of the chips in the'dump tank. These chipsare supported upon aperforatedbottom, which may be a lattice work as indicatedat 16, thewash liquor draining through the lattice work and escaping to sewer or.recovery through the p1pe 17 The dump tank 15 is provided with means forfeeding the softened and drained chips at a controlled rate to the rodmill. As illustrated, the bottom of the dump tank is pro- 7 vided withan opening 20 located adjacent the periphery of the tank. This openingis closed by a valve (not shown) during the dumping and washingoperations, and is then opened to permit the feeding of softened chips,at a controlled rate onto an endless conveyor 22. Positioned Within thedump tank is What is termed a leach caster. which comprises a centralvertical shaft 24 supported in suitable bearings and driven throughgears 25 and 26 from a drive shaft 27 which in turn is driven at acontrolledrate from any suitable source of power.

\ mounted on the shaft 24 for vertical movement thereon and is keyedthereto so as to rotate with the shaft 24. The stirring arm carries aplurality of depending inclined blades or fingers 31 which areconstructed to move the chips toward the periphery of the tank uponrotation oftheshaft 24 and arm 30. The construction is such that the armslides up and down the shaft 24 in accordance with the A stirring arm 30is slidablyv level of chips within the dump tank so that the arm restson the surfaceof the chips. The rate at which the chips are fed to theperiphery of the tank is controlled by the rate of rotation of the shaft24, this in turn control ling the rate at which the chips are fedthrough the opening 20 onto the conveyor 22. The conveyor 22 dischargeschips into a receiving hopper 35 feeding intoan endless bucket elevator36, which in turn discharges onto an endless conveyor 37 feeding intothe inlet 38 of a rod mill 40. controlled supply of dilution liquid,which is generally white water from the forming machine, is admittedconcomitantly with the softened chips through a supply pipe 42. Thedilution liquid is generally controlled to provide a stock consistencyof about 5% to 8% within the rod mill, this consistency range beingfound to be very satisfactory for the rod-milling-of pulp of thischaracter.

- The rod mill comprises an outer rotary shell 41 which containsthereina plurality of loose parallely arranged rods extending substantia lythroughout the length of the shell. The

contracted ends 43 and 44 of the shell are supported in suitablebearings (not shown), and the body of the shell is provided with anannular gear 45 which is driven through gearing from a suitable powershaft (not shown). The softened chips are simultaneously fed into theinlet 38 with dilution liquid from the pipe. 42, and the stock feedsfrom the inlet 38 to the discharge 44 as the casing 41 is rotated toprovide a tumbling and cascading of'the rods within the casing tothereby give a thorough pounding, rubbing and shredding treatment to thefibrous material. This serves to effectively pulp the softened chips andto hydrate the fibers without. objectionable cutting of the fibers.While a rod mill is disclosed herein, it is to be understood that othertypes of disintegrating mills can be used to give this effectivepounding, rubbing and shredding treatment, such,-for.example, as aswinghammer type of mill inwhich the pounding elements are mountedtherein-for swinging and impacting movement. In disintegrating mills ofthis character provided with swinging or loose impacting element's,*theunreduced bundles or lumps of fibrous material receive substantiallv theentire action of the movable elements. such as the rods, while theportions that are suflicientlv reduced are protected bythe lumps againstfurther reducion ,and cut ing action.

The weight of the rods within a rod mill and the speed of rotation ofthe mill are selected to provide for the most effective treatment. In amill having a shell 12 feet long and 6 feet in diameter, a weight of40,000 pounds of rods is found to give very satisfactory results whentreating leached chestnut chips. But this may be varied withinconsiderable limits to suit the characteristics of the particular pulpor fibrous material being treated. The speed of rotationof the rod millis preferably controlled so that the rods merely cascade or roll overone another and there is substantially no throwing or free falling 7 "ofthe rods. This cascading efl'ect gives the desireddisintegrating andhydrating treatment without the more-forceful collision effect of afreely falling rod which is apt to w cut the fibers. In a mill of thesize above mena-nce with the rate at which fresh material is fed intothe mill. the time of treatment within the rod mill beingthereby'controlled by the rate of feed. Inasmuch as the rate of feed iscontrolled by the leach caster of the dump tank, effective .control of.the time of treatment in the rod mill is obtained by con "trol of thespeed of rotation of the shaft 24 of the leach caster, which may beobtained by control of the speed of the drive shaft 27 in 30 anysuitable conventional manner, such as by a variable speed motor withrheostat control.

The discharge from the rod mill is fed to a stock chest 50 provided withsuitable agitating mechanism such as a driven horizontal shaft 51 havingstirring arms 52- At this point, additional dilution liquid, such aswhite water, may be added through a pipe 54 t reduce the consistency ofthe stock within the chest to a point such that it can be readilypuinpe'd'through conduits, a consistencv range of about 3% to 5% givingsatisfactory results. Stock is withdrawn from the chest 50 through pipe56 by a suitable pump such as a centrifugal pump57, which feeds itthrough pipe 58 to overflow box 60. This overflow box may be of anysuitable'and conventional construction adapted to regulate the supply ofstock to the jordan, the excess supplied by the pump 57 being returnedto the stock chest 50. As shown, the overflow tank 60 is divided bypartitions 61 and 62 into three compartments 63, 64 and 65. The pump 57feeds the stock through pipe 58 into the central compartment 64. Thecompartment 63 is connected by pipe 67 which returns the excess stock,to the stock chest 50. The compartment is connected by pipe 69 whichfeeds a regulated supply into the jordan 7 5. The partition 61 is of afixed height, while the partition 62'is provided with an adjustable weir70 to control the amount of stock feeding over the weir and thence tothe jordan. The provision of a stock chest inter mediate the rod milland jordan permits the 65 rod mill and jordan to be driven at separaterates, and to have different capacities, thus .out treatment to thestock passing therethrough serving to refine and separate suflicientlythe pulped material into its ultimate fibers. An adjusting shaftprovided with a hand wheel 81 is rotatably mounted in a fixedbearingtnot shown) and is threadedly received within the end wall of thecasing 76 to effect upon rotation of the shaft longitudina l adjustmentof the casing and plug relatively to each other, to secure the desiredsetting of the respective knives to regulate the degre of brushing-outtreatment effected by the jordan. As any conventional means maybe usedto control the jordan setting, further illustration is thoughtunnecessary. )Vhile a jordan is illustrated herein, it is to beunderstood that other types of refiners may be used, such as a claflin.

The stock treated in the jordan 75 discharges through pipe 85 into asecond stock chest 86 having an agitating shaft 87 and stirring arms 88.The stock is withdrawn from the chest 86 through pipe 89 by pump 90 andfed through pipe 91 to a second overflow .box 92 which is similar inconstruction to the overflow box 60. A regulated supply of stock is fedfrom the overflow box through pipe 94 to the inlet of a cylinder moldtank of a suitable forming machine (not shown), or to other treatingapparatus. The over flow from the box 92 passes through return pipe 95back to the stock chest 86. The construction is such that the overflowis returned to the system on the far side of the jordan so thatthisoverflow is not subjected again to a j ordaning treatment with theresult that the fibers are not shortened or cut up additionally, and thestock is uniformly treated.

In practice the operator at the forming machine tests the stock fromtime to time to determine its relative hardness or softness. This isdetermined in practice by the feel of the stock in the light ofthe'experience of the operator. If he finds, for example, that thecooked material received from the digester is a harder cook thanpreviously, the time of treatment in the rod mill is increased byreducing the rate of feed at the leach caster. At the same time, thejordaning treatment is coordinated therewith by proportionately freeingup the jordan setting to increase the clearance of the knives of theplug from the interior knives of the surrounding casing. Conversely,.when he finds the pulp softer than previously; the time of treatment inthe rod mill is reduced by speeding up the rate of feed of the leachcaster, and at the same d the following is given.

time the jordan setting is tightened up to reduce the clearance of theknives. By a proper coordination of the control of the respectivemechanical treatments, a stock of substantially uniform characteristicsis ob tained. The combination of the rod-milling treatment with thejordaning treatment for pulp of this character isfound to considerablyreduce the work on each machine, and the proper coordination as abovedescribed effects an increase in capacity of both machines as well as anincrease intbe quality of the pulp. An average yield of 70% to 85% onthe dry weight of the wood has been obtained by this method ,andapparatus in actual practice with leached chestnut chips; andcorrugating board produced from such chestnut chip pulp is found to besubstantially twice as strong as ordinary strawboard as heretoforemanufactured in the industry.

As an example of a pulping treatment carried out in accordance with thisinvention, A cooking liquor consisting of 1800 pounds of sodium sulphiteand 700 pounds of sodium bicarbonate (both calculated as sodiumcarbonate) is added to the digester together with 14,000 pounds of wood(dry basis), this charge practically filling the digester. The charge isbrought up to approximately 125 C. with steam, the cooking beingcontinued at this temperature for approximately two hours. Then theliquor in the digester is blown back into a closed receiving tank wherefresh liquor is added to bring it up to strength, and this liquor maythen be used to cook a second charge. The chips impregnated withtheliquor and which remain in the digester, are then steamed until thetemperature is brought upv to approximately 160 C., this temperaturetogether with the absorbed cooking liquor serving to effect thesoftening of the chips. This second stage of the cooking is generallycarried on for about f hours. While the cooking is generally carried outunder certain set conditions, certain variables enten in as abovedescribed, to give a cooked material which varies in characteristicswith different batches. The cooked chips are then dumped into the dumptank and washed, the plug valve for the outlet 20 being closed. The plugvalve is then opened and the shaft 24 of the leach caster driven to feedthe softened chips at a controlled rate to the rod mill 40. With a millof the size above mentioned, the rate. of feed of the chips is generallycontrolled to give an output of about 13 tons to 18 tons of rodmilledstock in 24 hours. The j ordan setting is coordinated therewith to givea regulated brushing-out treatment, the clearance between the bladesbeing generally varied between 0.005 of an-inch to about of an inch.-

erated at a rate of about 15 tons a day, and

the jordan is given an intermediate setting within the limits abovementioned. Should the cook from the digester be a hard cook, the

leach caster is slowed down-to provide fora reduced feeding rateapproaching 13 tons a day to the rod mill, and at the same time thejordan is given a freer setting by opening up the clearance to approacha clearance of about 1 3' of an inch. On the other hand, when a softcook is obtained from the digester, the time of treatment in the rodmill is reduced by increasing'the rate of feed to approach 18 tons .aday, and the jordan is tightenedup to reduce the clearance to approach.005 of an inch.

,While the method herein described, and the form of apparatus forcarrying this method into effect, constitute preferred -emprecise methodand'form of apparatus, and

that changes may be made ineither without departing. from the scope ofthe invention which is defined in the appended claims.

What is claimed is: 1. In the manufacture of pulp, the method whichcomprises cooking fibrous material with an incomplete chemical cookingtreatment to soften the fibrous material without pulping thereof,whereby a cooked material of characteristics varying substantially froma morevcompletely cooked -material or soft cook to a less completelycooked material or hard cook is produced, mechanically disintegratingthe softened and unpulped material, mechanically refining thedisintegrated material, and coordinating the disintegrating treatmentwith" the refining treatment in accordance with the character of thecooked material, by providing a more rigorous disin- I tegratingtreatment and a less rigorous refining treatment for a hard cook, and aless rigorous disintegrating treatment and a more rigorous refiningtreatment for a soft cook.

2. In the manufacture of pulp, the method which comprises cookingfibrous material with an incomplete chemical cooking treatment to softenthe fibrous material without pulping thereof, whereby a cooked materialof characteristics varying substantially from a more completely cookedmaterial or soft cook to a less completely cooked material or hard cookis produced, rod-milling the softened and unpulped material, jordaningthe rod-milled material, and coordinating the time of rod-millingtreatment with the degree of jordaning treatment in accordance with thecharacter of the cooked material, by providing a longer time ofrod-milling treatment and a freer setting of the jordan for a hard cook,and a shorter time of rodmilling treatment and a tighter setting of thejordan for a soft cook.

trolled rate, introducing the stream of ma-' terial of low moisturecontent concomitantly with dilution liquid into a rod mill, rodmillingthe cooked fibrous material admixed with dilution liquid, and controllngthe rate of feed and introduction of the drained material and theintroduction of the dilution liquid into the rod mill to thereby controlthe time of' rod-milling treatment.

4. Apparatus of the character described, comprising in combination, adump tank adapted to receive a mass of partially cooked undefiberedfibrous material and having provisions for efiecting draining ofmaterial received therein, rotary means for discharging .materialcontinuously from the mass of drained material in said dump tank, amechanical disintegrator, and means for continuously feeding thematerial discharged by said rotary means into said mechanicaldisintegrator.

5. Apparatus of the character described, comprising in combination, adump tank adapted to receive partially cooked undefibered' wood chipsand having provisions of chips received for effecting drainin therein,said dump tan having a discharge opening adjacent the periphery thereof,a rotary arm for continuously feeding drained alkali metal carbonate tosoften the wood without pulping while maintaining its chip form,subjecting the softened chip material to a mechanical disintegration bya pound ing treatment of impact elements, mechanically refining thedisintegrated material,

'and coordinating the disintegrating treatment with the refiningtreatment in accordance with the character of the cooked mate-- rial byproviding a more rigorous distinte- 5 gratingtreatment and a lessrigorous refining treatment for a h rd cook, and a less rigorousdisintegrating treatment and a more rigorous refining treatment for asoft cook. 7

8. In'the manufacture of pulp from wood 80 chips, the method. whichcomprises cooking the chips with an incomplete chemical cookingtreatment to soften the chips without pulping while maintaining the chipform thereof, dumping the cooked chips without blowing, permitting thecooked chips to drain, feeding the drained chips from the drained massin a continuously moving' stream of chips and at a controlled rate,introducing the softened chips and a dilution liquid concomitantly andcontinuously into a disintegrator, and mechanically disintegrating thesoftened chips in the prs ence of dilution liquid by a poundingtreatment o'fimpact elements.

In testimony whereof I hereto aflix my signature.

. WALTER J. ZIMMERMAN.

' chips from the mass confined in said dump tank through said" dischargeopening, a mechanical disintegrator, means for continuously introducingchips fed through said discharge opening into said mechanicaldisintegrator, and means for varying the rate of discharge feed of saidarm to thereby vary the rate of feed to said mechanical disintegrator.

6. Apparatus of the character described, comprising in combination, adump tank for receiving a mass of partially cooked unde fibered fibrousmaterial and for draining liquor from the same, means for dischargingdrained fibrous material at a controlled rate from the mass in. saiddump tank, means for continuously transporting drained material of lowmoisture content in a continuously Ill moving nonliquid stream,"adisintegrating mill, and means for concomitantly introducing thetransported material and dilution liquid into said disintegrating mill.I

7; In the manufacture of pulpjfrom hard deciduous wood,'such aschestnut, the method which comprises. cooking the deciduous wood in chipform with an incomplete chemical cooking treatment with a cooking liquorcontaining an alkali metal sulphite and an

